v0.17.1

StartUpDG v0.17.1

Diff since v0.17.0

Merged pull requests:

• Switch to concatenated nonconforming interface treatment (#140) (@jlchan)
• add is_periodic keyword argument to standard MeshData (#141) (@jlchan)
• Fix cut-cell MeshData type instability for geometric terms (#143) (@jlchan)